[Separate translation units] [th02] snd_mmd_resident() (undecompilable)

Reason: Wants to be word-aligned, and the previous version in OP.EXE,
game_exit(), is not, despite having an even length :(
Oh well, at least I'm confident enough about it by now to document it.
And out of all decompilations to be thrown away, this is a pretty
dispensable one.

Part of P0133, funded by [Anonymous].

Makefile.mak

@@ -78,17 +78,17 @@ bin\th02\zun_res.com: th02\zun_res1.c th02\zun_res2.c th02\zun_res3.c
 $**
 | masters.lib
 
-bin\th02\op.exe: th02\op_01.cpp bin\exit_dos.obj bin\th02\zunerror.obj bin\th02\grppsafx.obj bin\th02\op.obj th02\op_02_1.cpp bin\th02\pi_load.obj bin\th02\grp_rect.obj bin\frmdely2.obj th02\op_02_2.cpp bin\th02\snd_mode.obj bin\th02\snd_pmdr.obj bin\th02\snd_load.obj bin\th02\pi_put.obj bin\th02\snd_kaja.obj th02\op_02_3.cpp bin\th02\snd_se.obj bin\frmdely1.obj th02\op_03.cpp th02\op_04.cpp th02\op_05.cpp th02\op_06.cpp
+bin\th02\op.exe: th02\op_01.cpp bin\exit_dos.obj bin\th02\zunerror.obj bin\th02\grppsafx.obj bin\th02\op.obj th02\op_02_1.cpp bin\th02\pi_load.obj bin\th02\grp_rect.obj bin\frmdely2.obj th02\op_02_2.cpp bin\th02\snd_mmdr.obj bin\th02\snd_mode.obj bin\th02\snd_pmdr.obj bin\th02\snd_load.obj bin\th02\pi_put.obj bin\th02\snd_kaja.obj th02\op_02_3.cpp bin\th02\snd_se.obj bin\frmdely1.obj th02\op_03.cpp th02\op_04.cpp th02\op_05.cpp th02\op_06.cpp
 	$(CC) $(CFLAGS) -ml -Z -DGAME=2 -nbin\th02\ -eOP.EXE @&&|
 $**
 |
 
-bin\th02\main.exe: bin\th02\main.obj bin\th02\zunerror.obj th02\main02_1.cpp bin\th02\pi_load.obj bin\th02\vector.obj bin\frmdely1.obj th02\main02_2.cpp bin\th02\snd_mode.obj bin\th02\snd_pmdr.obj bin\th02\snd_dlyv.obj bin\th02\snd_load.obj th02\mptn_i.cpp bin\th02\initmain.obj bin\th02\pi_put.obj bin\th02\snd_kaja.obj bin\th02\snd_dlym.obj bin\th02\snd_se.obj th02\main_03.cpp
+bin\th02\main.exe: bin\th02\main.obj bin\th02\zunerror.obj th02\main02_1.cpp bin\th02\pi_load.obj bin\th02\vector.obj bin\frmdely1.obj th02\main02_2.cpp bin\th02\snd_mmdr.obj bin\th02\snd_mode.obj bin\th02\snd_pmdr.obj bin\th02\snd_dlyv.obj bin\th02\snd_load.obj th02\mptn_i.cpp bin\th02\initmain.obj bin\th02\pi_put.obj bin\th02\snd_kaja.obj bin\th02\snd_dlym.obj bin\th02\snd_se.obj th02\main_03.cpp
 	$(CC) $(CFLAGS) -ml -Z -DGAME=2 -nbin\th02\ -eMAIN.EXE @&&|
 $**
 |
 
-bin\th02\maine.exe: bin\th02\maine.obj bin\th02\grppsafx.obj th02\maine021.cpp bin\th02\pi_load.obj bin\frmdely1.obj th02\maine022.cpp bin\th02\snd_mode.obj bin\th02\snd_pmdr.obj bin\th02\snd_load.obj bin\th02\initmain.obj bin\th02\pi_put.obj bin\th02\snd_kaja.obj bin\th02\snd_dlym.obj th02\maine_03.c th02\maine_04.cpp th02\maine_05.cpp
+bin\th02\maine.exe: bin\th02\maine.obj bin\th02\grppsafx.obj th02\maine021.cpp bin\th02\pi_load.obj bin\frmdely1.obj th02\maine022.cpp bin\th02\snd_mmdr.obj bin\th02\snd_mode.obj bin\th02\snd_pmdr.obj bin\th02\snd_load.obj bin\th02\initmain.obj bin\th02\pi_put.obj bin\th02\snd_kaja.obj bin\th02\snd_dlym.obj th02\maine_03.c th02\maine_04.cpp th02\maine_05.cpp
 	$(CC) $(CFLAGS) -ml -3 -Z -DGAME=2 -nbin\th02\ -eMAINE.EXE @&&|
 $**
 |

Research/Borland C++ decompilation.md

@@ -368,6 +368,19 @@ static_storage  db  2, 0, 6
 @_STCON_$qv	endp
 ```
 
+
+## Padding bytes in code segments
+
+- `0x00` is only emitted to word-align `switch` jump tables with `-a2`.
+  Anywhere else, it indicates the start or end of a word-aligned `SEGMENT`
+  compiled from assembly. Borland C++ never adds padding between functions or
+  segments.
+
+  **Certainty**: Would love to find a proper compiler or linker setting for
+  this, but it doesn't seem to exist. The `#pragma codestring \x00` workaround
+  doesn't respect different alignment requirements of surrounding translation
+  units, after all.
+
 ## C++
 
 In C++ mode, the value of a `const` scalar-type variable declared at global

Tupfile

@@ -68,6 +68,7 @@ BMP2ARR = bin\\Pipeline\\bmp2arr.exe
 
 : th02_zuninit.asm |> !as |> bin\\th02\\zuninit.obj
 : th02\\snd_se.asm |> !as2 |>
+: th02\\snd_mmdr.asm |> !as2 |>
 : th02_op.asm |> !as |> bin\\th02\\op.obj
 : th02_main.asm | \
 	th02/sprites/pellet.asp \

Tupfile.bat

@@ -25,6 +25,7 @@ tasm32 /m /mx /kh32768 /t th01_reiiden.asm bin\th01\reiiden.obj
 tasm32 /m /mx /kh32768 /t th01_fuuin.asm bin\th01\fuuin.obj
 tasm32 /m /mx /kh32768 /t th02_zuninit.asm bin\th02\zuninit.obj
 tasm32 /m /mx /kh32768 /t /dGAME=2 th02\snd_se.asm bin\th02\snd_se.obj
+tasm32 /m /mx /kh32768 /t /dGAME=2 th02\snd_mmdr.asm bin\th02\snd_mmdr.obj
 tasm32 /m /mx /kh32768 /t th02_op.asm bin\th02\op.obj
 tasm32 /m /mx /kh32768 /t th02_main.asm bin\th02\main.obj
 tasm32 /m /mx /kh32768 /t th02_maine.asm bin\th02\maine.obj

th02/main02_2.cpp

@@ -8,14 +8,11 @@
 
 extern "C" {
 #include <dos.h>
-#include "libs/kaja/kaja.h"
 #include "th02/th02.h"
 #include "master.hpp"
 #include "th02/hardware/frmdelay.h"
 #include "th02/hardware/input.hpp"
-#include "th02/snd/snd.h"
 
 #include "th02/hardware/input.c"
 #include "th02/exit.c"
-#include "th02/snd/mmd_res.c"
 }

th02/maine022.cpp

@@ -7,12 +7,10 @@
 
 extern "C" {
 #include <dos.h>
-#include "libs/kaja/kaja.h"
 #include "th02/th02.h"
 #include "master.hpp"
 #include "th02/hardware/frmdelay.h"
 #include "th02/hardware/input.hpp"
-#include "th02/snd/snd.h"
 #include "th02/formats/pf.hpp"
 
 #include "th02/snd/data.c"
@@ -20,5 +18,4 @@ extern const char pf_fn[] = PF_FN;
 
 #include "th02/hardware/input.c"
 #include "th02/exit.c"
-#include "th02/snd/mmd_res.c"
 }

th02/op_02_2.cpp

@@ -8,12 +8,10 @@
 
 extern "C" {
 #include <dos.h>
-#include "libs/kaja/kaja.h"
 #include "th02/th02.h"
 #include "master.hpp"
 #include "th02/mem.h"
 #include "th02/core/initexit.h"
-#include "th02/snd/snd.h"
 #include "th02/formats/pf.hpp"
 #include "th02/hardware/frmdelay.h"
 #include "th02/hardware/input.hpp"
@@ -25,8 +23,4 @@ const char pf_fn[] = PF_FN;
 #include "th02/hardware/input.c"
 #include "th02/core/initop.cpp"
 #include "th02/exit.c"
-
-#pragma codestring "\x00"
-
-#include "th02/snd/mmd_res.c"
 }

th02/snd/mmd_res.asm

@@ -2,7 +2,7 @@ public _snd_mmd_resident
 _snd_mmd_resident proc
 	xor	ax, ax
 	mov	es, ax
-	les	bx, dword ptr es:[61h * 4]
+	les	bx, dword ptr es:[MMD * 4]
 	assume es:nothing
 	cmp	byte ptr es:[bx+2], 'M'
 	jnz	short @@nope
@@ -10,7 +10,7 @@ _snd_mmd_resident proc
 	jnz	short @@nope
 	cmp	byte ptr es:[bx+4], 'D'
 	jnz	short @@nope
-	mov	_snd_interrupt_if_midi, 61h
+	mov	_snd_interrupt_if_midi, MMD
 if GAME le 3
 	mov	_snd_midi_active, 1
 endif
@@ -25,4 +25,4 @@ endif
 	xor	ax, ax
 	ret
 _snd_mmd_resident endp
-	nop	; word alignment
+	even

th02/snd/mmd_res.c

@@ -1,23 +0,0 @@
-#pragma option -k-
-
-int snd_mmd_resident(void)
-{
-	_AX = 0;
-	__asm	mov es, ax;
-	__asm	les bx, dword ptr es:[MMD * 4];
-	__asm	cmp byte ptr es:[bx+2], 'M';
-	__asm	jnz nope;
-	__asm	cmp byte ptr es:[bx+3], 'M';
-	__asm	jnz nope;
-	__asm	cmp byte ptr es:[bx+4], 'D';
-	__asm	jnz nope;
-	snd_interrupt_if_midi = MMD;
-	snd_midi_active = 1;
-	snd_midi_possible = 1;
-	return 1;
-nope:
-	snd_midi_possible = 0;
-	return 0;
-}
-
-#pragma codestring "\x90"

th02/snd/snd.h

@@ -27,8 +27,10 @@ extern bool snd_midi_possible;
 // check for an actual installed FM sound source is done by
 // snd_determine_mode().
 bool16 snd_pmd_resident(void);
-#if GAME != 3
-	int snd_mmd_resident(void);
+#if (GAME != 3)
+	// Returns whether the MMD driver is resident at its interrupt. If it is,
+	// ≤TH03 sets [snd_midi_active] to true.
+	bool16 snd_mmd_resident(void);
 #endif
 
 // Checks whether an FM sound source is active, and sets [snd_fm_possible]

th02/snd_mmdr.asm

@@ -0,0 +1,16 @@
+	.386
+	.model large SHARED
+	locals
+
+include libs/kaja/kaja.inc
+
+	extrn _snd_interrupt_if_midi:byte
+	extrn _snd_midi_active:byte
+	extrn _snd_midi_possible:byte
+
+SHARED	segment word public 'CODE' use16
+	assume cs:SHARED
+include th02/snd/mmd_res.asm
+SHARED	ends
+
+	end